To detect combustible gases in industries, it is important to choose a safe, dependable and affordable solution. There are two main technologies involved; they are infrared (IR) sensors and catalytic sensors. Each method has its advantages depending on the application.
A thorough analysis of the unique field of application is required to ensure safety, optimal performance, reliability and cost-effectiveness. A wrong decision will compromise the performance, safety, and maintenance costs, and will affect the durability of your detector.
Catalytic sensors represent a big number of gas detection devices being manufactured today. They are used in detecting combustible gases such as hydrocarbons, and they work through catalytic oxidation.
The sensors in the detector are made using wire coils treated with platinum. As the catalytic surface comes into contact with a combustible gas, it is oxidized, and the resistance of the wire changes because of the heat released. A bridge circuit is used as an indicator of the resistance change, which is proportional to the quantity of gas present.
Advantages of Catalytic Sensors
Catalytic sensors have several significant advantages because they are:
- Easy to operate
- Simple to install, calibrate and use
- Durable with a low cost of maintenance
- Proven technology that is reliable and predictable
- Easy to calibrate to individual gases
Disadvantages of Catalytic Sensors
Catalytic sensors also have some disadvantages because:
- Catalysts become contaminated, thus deterring their functionality
- The only method of identifying the loss of detector sensitivity due to catalytic poisons is to use the appropriate gas on a regular basis, and this requires calibration
- They require oxygen for detection
- Prolonged exposure to high concentrations of combustible gas may impair the sensor performance
IR sensors work through a system of transmitters and receivers in detecting combustible gases. Usually, the transmitters are the sources of light, and the receivers are the light detectors. The presence of gas in the optical path interferes with the strength of transmission between the transmitter and the receiver. A change in the state of light will determine the presence and the type of gas present.
Advantages of Infrared Sensors
IR sensors have several advantages because they:
- Need less regular calibration
- Are immune to contamination and poisoning
- Can operate in the presence or absence of oxygen
- Can detect at levels above 100 LEL
- Can work in a continuous presence of gases
Disadvantages of Infrared Sensors
The disadvantages of IR sensors are:
- The Gas being measured must be infrared active
- Optimal temperature for detection is 70ºC
- It requires a considerably large volume of gas for response testing
- To replace the IR source, the system must be returned to the manufacturer
- It doesn’t work well for multiple gas applications
There is an evident need for both catalytic and IR detectors in the industries. To make an informed choice, consider the application field environment and the sensor design variables. This requires you to be keen in analyzing the detectors, and your field experience will help you to choose the best detector to suit your needs.